This investigation aims to examine the efficacy of a cognitive-behavioral treatment for nocturnal panic attacks in persons with Panic Disorder/Agoraphobia. Also included are specific investigations of cognitive-attributions as they relate to nocturnal panic, and the relationship between nocturnal panic and measures of physiological arousal during sleep. Furthermore, the study aims to identify factors that may predict the occurrence of nocturnal panic. Nocturnal panic is experienced by almost half of persons with Panic Disorder/Agoraphobia, and yet very little is known about its course or its treatment. After full sleep polysomnogram screening, subjects with recent recurrent nocturnal panics will be randomly assigned to a cognitive-behavioral intervention (tailored specifically to nocturnal panic) versus a wait-list control condition. Pre and post measures include clinician ratings, self- ratings of psychological functioning, self-monitoring- of anxiety and panic, responses to laboratory tasks, and sleep physiology (via ambulatory recording). At completion of the wait-list, subjects in this condition will receive cognitive-behavioral therapy in a type of replication design. in addition, a nine-month follow-up assessment is included to measure the stability of gains. As part of the pre-treatment assessment, subjects will undergo a laboratory assessment designed to examine specific cognitive sets about physiological events that occur during sleep. Subjects will be randomly assigned to "safety" or "no-safety" conditions. The study will measure subjective, behavioral, and physiological responses to an audio signal that ostensibly reflects normal and expected (safety) versus unexpected and strong (no-safety) physiological events. The results of this investigation pertain to the cognitive-behavioral conceptualization of nocturnal panic. Finally, panickers who have never experienced nocturnal panic will be compared to the nocturnal panic sample in terms of cognitive aspects, physiological aspects, sleep history, and general distress, to identify factors that predict nocturnal panic, especially those that are consistent with the cognitive-behavioral conceptualization of nocturnal panic.